Laser weld coaxial connector and interconnection method

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by laser welding is provided with a monolithic connector body with a bore. A sidewall of the bore is provided with an inward annular projection angled toward a cable end of the bore. A sidewall of the inward annular projection and the sidewall of the bore form an annular laser groove open to a cable end of the bore. The annular laser groove is dimensioned with a taper at a connector end of the laser groove less than a thickness of a leading end of the outer conductor. The taper provides an annular material chamber between the leading end of the outer conductor, when seated in the laser groove, and the connector end of the laser groove.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. Moreparticularly, the invention relates to a coaxial cable connectorinterconnectable via laser welding.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systemsrequiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnectionbetween the cable and the connector, it is desirable to have generallyuniform, circumferential contact between a leading edge of the coaxialcable outer conductor and the connector body. A flared end of the outerconductor may be clamped against an annular wedge surface of theconnector body via a coupling body. Representative of this technology iscommonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz.Although this type of connector is typically removable/re-useable,manufacturing and installation is complicated by the multiple separateinternal elements required, interconnecting threads and relatedenvironmental seals.

Connectors configured for permanent interconnection via solder and/oradhesive interconnection are also well known in the art. Representativeof this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep.8, 1998 to Bufanda et al.

However, solder and/or adhesive interconnections may be difficult toapply with high levels of quality control, resulting in interconnectionsthat may be less than satisfactory, for example when exposed tovibration and/or corrosion over time.

Competition in the coaxial cable connector market has focused attentionon improving electrical performance and long term reliability of thecable to connector interconnection. Further, reduction of overall costs,including materials, training and installation costs, is a significantfactor for commercial success.

Therefore, it is an object of the invention to provide a coaxialconnector and method of interconnection that overcomes deficiencies inthe prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention,where like reference numbers in the drawing figures refer to the samefeature or element and may not be described in detail for every drawingfigure in which they appear and, together with a general description ofthe invention given above, and the detailed description of theembodiments given below, serve to explain the principles of theinvention.

FIG. 1 is a schematic external isometric view of an exemplary embodimentof a coaxial connector installed upon a coaxial cable with a couplingnut spaced away from the connector along the cable forconnector-to-cable interconnection.

FIG. 2 is a schematic isometric view of the coaxial connector of FIG. 1installed upon a coaxial cable, with the coupling nut seated upon thecoaxial connector.

FIG. 3 is a schematic isometric view of the coaxial connector of FIG. 1.

FIG. 4 is a schematic cross section side view of FIG. 2.

FIG. 5 is an enlarged view of area A of FIG. 4.

FIG. 6 is a schematic exploded isometric partial cut-away view of theconnector and cable of FIG. 1.

FIG. 7 is a schematic isometric partial cut-away view of the connectorbody of FIG. 5.

FIG. 8 is a schematic isometric view of an alternative connector bodywith notches on a flange of the connector body.

FIG. 9 is a schematic isometric view of an alternative connector bodywith longitudinal knurls on the connector body outer diameter.

FIG. 10 is a schematic isometric cut-away view of the overbody of FIG.5.

FIG. 11 is an enlarged view of area B of FIG. 4.

FIG. 12 is a schematic cross section side view of an alternativeoverbody with corrugation on an inner diameter of the cable end.

FIG. 13 is a schematic cross section side view of an alternativeoverbody with a stepped surface on an inner diameter of the cable end.

FIG. 14 is a schematic cross section side view of a coaxial connectorembodiment with an inner conductor end cap.

FIG. 15 is a schematic cross section side view of the coaxial connectorof FIG. 4 demonstrating a laser beam path during laser welding.

FIG. 16 is an enlarged view of area E of FIG. 15.

FIG. 17 is a schematic cross section side view of an alternativeembodiment of a coaxial connector for laser welding interconnection.

FIG. 18 is an enlarged view of area C of FIG. 17.

FIG. 19 is a schematic cross section side view of the coaxial connectorof FIG. 17 demonstrating a laser beam path during laser welding.

FIG. 20 is an enlarged view of area D of FIG. 19.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper forthe conductors in coaxial cables. However, aluminum oxide surfacecoatings quickly form upon air-exposed aluminum surfaces. These aluminumoxide surface coatings may degrade traditional mechanical, solder and/orconductive adhesive interconnections.

The inventors have recognized that increasing acceptance of coaxialcable with solid outer conductors of aluminum and/or aluminum alloyenables connectors configured for interconnection via laser weldingbetween the outer conductor and a connector body which may also be costeffectively provided, for example, formed from aluminum and/or aluminumalloy.

An exemplary embodiment of a laser weldable coaxial connector 2 isdemonstrated in FIGS. 1-4. As best shown in FIG. 4, a unitary connectorbody 4 is provided with a bore 6 dimensioned to receive the leading edgeof the outer conductor 8 of a coaxial cable 9 therethrough. Positionedfor interconnection by laser welding, the leading edge of the outerconductor 8 extends through the bore 6 to a longitudinal positiongenerally flush with the edge of a shoulder 10 of the connectioninterface 14 at the connector end 18, presenting a common end face tothe connector end 18, as best shown in FIG. 5. The connection interface14 may be any desired standard or proprietary connection interface 14which includes access to a circumferential contact seam 16 between thebore 6 and the outer conductor 8, the seam 16 generally parallel to alongitudinal axis of the coaxial connector 2.

One skilled in the art will appreciate that connector end 18 and cableend 12 are applied herein as identifiers for respective ends of both thecoaxial connector 2 and also of discrete elements of the coaxialconnector 2 described herein, to identify the same and their respectiveinterconnecting surfaces according to their alignment along alongitudinal axis of the coaxial connector 2 between a connector end 18and a cable end 12.

Where the diameter of the bore 6 is selected with respect to thediameter of the outer conductor 8 to be a close tolerance fit, laserwelding interconnection of the outer conductor 8 and the connector body2 may be performed without the addition of further material, such aswelding rod or wire. The high level of localized heating from the laser,applied to the seam 16 between the outer conductor 8 and the connectorbody 2, may be applied as a pulse directed to a target spot, withsuccessive pulses applied to an overlapping spot portion to form acontinuous weld between adjacent portions of the outer conductor 8 andthe connector body 2.

Prior to interconnection via laser welding, the end of the cable 9 maybe prepared, as best shown in FIG. 6, by cutting the cable 9 so that theinner conductor 24 extends from the outer conductor 8. Also, dielectricmaterial 26 between the inner conductor 24 and outer conductor 8 may bestripped back and a length of the outer jacket 28 removed to exposedesired lengths of each. A portion of the dielectric material 26 may beprovided extending forward of the leading edge of the outer conductor 8,for example as an interconnection impedance discontinuity reductionfeature.

Where applicable, the cable end preparation may also include the step ofstraightening the cable end portion, for example to eliminate anybending in the cable resulting from bulk cable delivery of the cablewound in spools, so that when inserted into the bore 6, the cable end iscoaxial with the bore 6 along its length and the inner conductor 24projects from the connector end 18 parallel to the longitudinal axis ofthe bore 6. Thereby, the seam between the bore sidewall 20 and the outerdiameter of the outer conductor 8 will be uniform around thecircumference of the outer conductor 8, increasing the uniformity of theresulting laser weld.

Because the localized heat of the laser welding process can disruptaluminum oxide surface coatings in the immediate weld area, noadditional care may be required with respect to removing or otherwisemanaging the presence of aluminum oxide on the interconnection surfaces.

An overbody 30, as shown for example in FIG. 10, may be applied to theconnector body 4 as an overmolding of polymeric material. The overbody30 increases cable to connector torsion and pull resistance. Theoverbody 30 may also provide connection interface structure at theconnector end 18 and further reinforcing support at the cable end 12,enabling significant reductions in the size of the connector body 4,thereby reducing overall material costs.

Depending upon the applied connection interface 14, demonstrated in theexemplary embodiments herein as a standard 7/16 DIN interface, theoverbody 30 may be provided with an overbody flange 32 and longitudinalsupport ridges 34 for a coupling nut 36. The coupling nut 36 is retainedupon the support ridges 34 at the connector end 18 by an overbody flange32 and at the cable end 12 by a retention spur 38 provided on at leastone of the support ridges 34. The retention spur 38 may be angled towardthe connector end 18, allowing the coupling nut 36 to be placed over thecable 9 initially spaced away from the coaxial connector 2 duringinterconnection (see FIG. 1), but then allowing the coupling nut 36 tobe passed over the retention spur 38 and onto the support ridges 34 fromthe cable end 12, to be thereafter retained upon the support ridges 34by the retention spur(s) 38 (see FIG. 2) in close proximity to theconnector interface 14 for connector to connector mating. The supportridges 34 reduce polymeric material requirements of the overbody 30while providing lateral strength to the connector/interconnection 2 aswell as alignment and retention of the coupling nut 36.

The overbody 30 may also extend from the connector end 18 of theconnector body 4 to provide portions of the selected connectioninterface 14, such as an alignment cylinder 39 of the 7/16 DINinterface, further reducing metal material requirements of the connectorbody 4.

The overbody flange 32 may be securely keyed to a connector body flange40 of the connector body 4 and thereby with the connector body 4 via oneor more interlock apertures 42 such as holes, longitudinal knurls 43,grooves, notches 45 or the like provided in the connector body flange 40and/or outer diameter of the connector body 4, as demonstrated in FIGS.7-9. Thereby, as the polymeric material of the overbody 30 flows intothe interlock apertures 42 during overmolding, upon curing the overbody30, for example as shown in FIG. 10, is permanently coupled to androtationally interlocked with the connector body 4.

As best shown in FIG. 11, the cable end 12 of the overbody 30 may bedimensioned with an inner diameter friction surface 44 proximate that ofthe coaxial cable outer jacket 28, enabling polymeric friction weldingbetween the overbody 30 and the outer jacket 28 prior to laser weldingof the connector body 4 and outer conductor, thereby eliminating theneed for environmental seals at the cable end 12 of the connector/cableinterconnection. During friction welding, the coaxial connector 2 isrotated with respect to the cable 9. Friction between the frictionsurface 44 and the outer diameter of the outer jacket 28 heats therespective surfaces to a point where they begin to soften andintermingle, sealing them against one another. To provide enhancedfriction and allow voids for excess flow due to friction displacementand add key locking for additional strength, the outer jacket 28 and/orthe inner diameter of the overbody 30 may be provided as a series ofspaced apart annular peaks of a contour pattern such as a corrugation46, as shown for example in FIG. 12, or a stepped surface 48, as shownfor example in FIG. 13. Alternatively, the overbody 30 may be sealedagainst the outer jacket 28 with an adhesive/sealant or may beovermolded upon the connector body 4 after interconnection with theouter conductor 8, the heat of the injected polymeric material bondingthe overbody 30 with and/or sealing against the outer jacket 28.

The inner conductor 24 extending from the prepared end of the coaxialcable 9 may be selected to pass through to the connector end 18 as aportion of the selected connection interface 14, for example as shown inFIG. 8. If the selected coaxial cable 9 has an inner conductor 24 thathas a larger diameter than the inner conductor portion of the selectedconnection interface 14, the inner conductor 24 may be ground at theconnector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageouslyeliminates interconnections, for example with the spring basket of atraditional coaxial connector inner contact, such may introduceelectrical performance degradation such as PIM. Where the innerconductor 24 is also aluminum material some applications may require anon-aluminum material connection point at the inner contact/innerconductor of the connection interface 14. As shown for example in FIG.14, a center cap 50, for example formed from a metal such as brass orother desired metal, may be applied to the end of the inner conductor24, also by laser or friction welding. To apply the center cap 50, theend of the inner conductor 24 is ground to provide a pin correspondingto the selected socket geometry of the center cap 50. To allow materialinter-flow during welding attachment, the socket geometry of the centercap 50 and or the end of the inner conductor 24 may be formed to provideannular material gaps 22.

Laser welding apparatus may be provided with a fiber optic laser headextension which may be adjusted to aim the laser beam B at each targetlocation along the seam 16. Alternatively, the coaxial connector 2, uponwhich the target location resides, may be maneuvered to align the targetlocation with respect to the laser head 54. A laser head 54 typicallyincludes a collimator 56 and a focus lens 58 which focuses the laserbeam B upon a focal point F at the target location. As shown in FIG. 15,the laser beam B extent has clearance requirements prior to reaching thefocal point F which are satisfied by the connector end 18 facingorientation of the seam 16 in the exemplary embodiment.

Prior to and once beyond the focal point F, the laser beam B has anincreasing diameter, progressively diminishing the effective power ofthe beam at longitudinal locations other than the focal point F. Tomaximize heat generation for welding, the laser head 54 may bepositioned with respect to the seam 16, such that the focal point F isbelow the seam 16 outer face, for example as shown in FIG. 16. Thereby,the highest power level is obtained as a molten area of the boresidewall 20 and the outer diameter of the outer conductor 8 is formedwithin the seam 16, rather than only along the outermost surface of theseam 16, resulting in a weld with greater depth and strength.

In further embodiments, for example as shown in FIGS. 17 and 18, thebore 6 may be provided with an inward projecting stop shoulder 52proximate the connector end 18 against which the outer conductor 8 abutsto form an inward facing circumferential seam 16 between the outerconductor 8 and the stop shoulder 52. The seam 16 is provided generallynormal to a longitudinal axis of the coaxial connector 2. As shown inFIGS. 19 and 20, the ability of the laser beam B to reach the seam 16without interference from the inner conductor 24 is a function of thecoaxial cable dimensions and the distance from the connection interface14 within the bore 6 at which the seam 16 is located.

In addition to increased adjustment requirements for the laser beam tofollow the inner circumference of the seam 16, the present embodimentalso requires removal of additional dielectric material 26, which maygenerate impedance discontinuity issues addressable by the addition offurther impedance tuning features, such as dielectric spacers or thelike.

One skilled in the art will appreciate that the connector andinterconnection method disclosed has significant material costefficiencies and provides a permanently sealed interconnection withreduced size and/or weight requirements.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outerconductor 9 cable 10 shoulder 12 cable end 14 connection interface 16seam 18 connector end 20 bore sidewall 22 material gap 24 innerconductor 26 dielectric material 28 outer jacket 30 overbody 32 overbodyflange 34 support ridge 36 coupling nut 38 retention spur 39 alignmentcylinder 40 connector body flange 42 interlock aperture 43 longitudinalknurl 44 friction surface 45 notch 46 corrugation 48 stepped surface 50center cap 52 stop shoulder 54 laser head 56 collimator 58 focus lens

Where in the foregoing description reference has been made to materials,ratios, integers or components having known equivalents then suchequivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

We claim:
 1. A method for interconnecting a coaxial connector with asolid outer conductor coaxial cable, the coaxial cable provided with aninner conductor supported coaxially within a thin cylindrical sidewallof the solid outer conductor by a dielectric material, comprising thesteps of: providing a monolithic connector body with a bore; inserting aleading end of the outer conductor into the bore, and laser welding acircumferential seam between the outer conductor and an inner diameterof the bore from a connector end of the connector body.
 2. The method ofclaim 1, wherein the outer conductor and the connector body are each oneof aluminum and aluminum alloy material.
 3. The method of claim 1,wherein the leading end of the coaxial cable is inserted into the boreuntil the outer conductor is generally flush with an edge of a shoulderof a connection interface at a connector end of the connector; thecircumferential seam parallel to a longitudinal axis of the connector.4. The method of claim 1, wherein the leading end of the coaxial cableis inserted into the bore until a leading edge of the outer conductorabuts a stop shoulder proximate a connector end of the bore; thecircumferential seam normal to a longitudinal axis of the connector. 5.The method of claim 1, further including the step of overmolding theconnector body attached to the end of the coaxial cable with a polymericoverbody.
 6. The method of claim 1, further including the steps ofpreparing the leading end of the cable end prior to insertion into thebore by removing a portion of the outer conductor so that an innerconductor extends therefrom, removing a portion of a dielectric materialbetween the inner conductor and the outer conductor such that dielectricmaterial extends forward of the leading edge of the outer conductor; andstripping back a portion of a jacket from the outer conductor.
 7. Themethod of claim 1, further including the steps of preparing the leadingend of the cable end prior to insertion into the bore by removing aportion of the outer conductor so that an inner conductor extendstherefrom, removing a portion of a dielectric material between the innerconductor and the outer conductor such that the dielectric material isrecessed within the leading end of the coaxial cable.
 8. The method ofclaim 1, further including providing an overbody of polymeric materialupon an outer diameter of the connector body, the overbody extendingfrom the cable end of the connector body, an inner diameter of theoverbody extending from the cable end of the connector body provided asa friction surface dimensioned for an interference fit upon an outerdiameter of a jacket of the coaxial cable.
 9. A method forinterconnecting a coaxial connector with a solid outer conductor coaxialcable, comprising the steps of: providing a monolithic connector bodywith a bore; providing an overbody of polymeric material upon an outerdiameter of the connector body, the overbody extending from the cableend of the connector body, an inner diameter of the overbody extendingfrom the cable end of the connector body provided as a friction surfacedimensioned for an interference fit upon an outer diameter of a jacketof the coaxial cable; inserting a leading end of the outer conductorinto the bore, rotating the connector with respect to the coaxial cableto form a friction weld between the overbody and the jacket of thecoaxial cable; and laser welding a circumferential seam between theouter conductor and the connector body.
 10. The method of claim 1,wherein the laser welding is applied with a focal point of a laser beampositioned below a surface of the seam.
 11. The method of claim 1,wherein the laser welding is applied as a plurality of spot welds withadjacent spot welds applied partially overlapping one another.
 12. Themethod of claim 1, wherein a head coupled to a laser by fiber opticcable is adjusted with respect to the circumferential seam to apply thelaser welding.
 13. The method of claim 1 wherein the circumferentialseam is manipulated with respect to a laser beam to apply the laserwelding.